Achieving an adequate B12 intake is easy and there
are several methods to suit individual preferences. Absorption of B12 varies from about 50%, if about 1
microgram or less is consumed, to about 0.5% for doses of 1000 micrograms (1 milligram) or above. So the
less frequently you consume B12, the higher the total amount needs to be to give the desired absorbed
amount.

Frequent use of foods fortified with B12 so that
about one microgram of B12 is consumed three times a day with a few hours in between will provide an
adequate amount. Availability of fortified foods varies from country to country and amounts of B12 vary
from brand to brand, so ensuring an adequate B12 supply from fortified foods requires some label reading
and thought to work out an adequate pattern to suit individual tastes and local products.

Taking a B12 supplement containing ten micrograms or
more daily provides a similar absorbed amount to consuming one microgram on three occasions through the
day. This may be the most economical method as a single high potency tablet can be consumed bit by bit.
2000 micrograms of B12 consumed once a week would also provide an adequate intake. Any B12 supplement
tablet should be chewed or allowed to dissolve in the mouth to enhance absorption. Tablets should be kept
in an opaque container. As with any supplement it is prudent not to take more than is required for maximum
benefit, so intakes above 5000 micrograms per week should be avoided despite lack of evidence for toxicity
from higher amounts.

All three options above should meet the needs of the
vast majority of people with normal B12 metabolism. Individuals with impaired B12 absorption may find that
the third method, 2000 micrograms once a week, works best as it does not rely on normal intrinsic factor in
the gut. There are other, very rare, metabolic defects that require completely different approaches to
meeting B12 requirements. If you have any reason to suspect a serious health problem seek medical advice
promptly.

Symptoms of B12 deficiency

Clinical deficiency can cause anaemia or nervous
system damage. Most vegans consume enough B12 to avoid clinical deficiency. Two subgroups of vegans are at
particular risk of B12 deficiency: long-term vegans who avoid common fortified foods (such as raw food
vegans or macrobiotic vegans) and breastfed infants of vegan mothers whose own intake of B12 is
low.